1. Field of the Invention
The present invention relates to the concurrent selective hydrogenation of vinylacetylene, ethylacetylene and 1,2-butadiene in an olefin rich C.sub.4 stream. More particularly the invention relates to a process utilizing hydrogenation catalysts in a structure to serve as both the catalyst and as a distillation structure for the simultaneous reaction and separation of the reactants and reaction products.
2. Related Information
Petroleum distillate streams contain a variety of organic chemical components. Generally the streams are defined by their boiling ranges which determine the compositions. The processing of the streams also affects the composition. For instance, products from either catalytic cracking or thermal cracking processes contain high concentrations of olefinic materials as well as saturated (alkanes) materials and polyunsaturated materials (diolefins). Additionally, these components may be any of the various isomers of the compounds.
Refinery streams contain a broad spectrum of olefinic compounds. This is especially true of products from either catalytic cracking or thermal cracking processes. These unsaturated compounds comprise ethylene, acetylene, propylene, propadiene, methyl acetylene, butenes, butadiene, amylenes, hexenes etc. Many of these compounds are valuable, especially as feed stocks for chemical products. Ethylene, especially is recovered. Additionally, propylene and the butenes are valuable. However, the olefins having more than one double bond and the acetylenic compounds (having a triple bond) have lesser uses and are detrimental to many of the chemical processes in which the single double bond compounds are used, for example, polymerization. Over the range of hydrocarbons under consideration, the removal of highly unsaturated compounds is of value as a feed pretreatment since these compounds have frequently been found to be detrimental in most processing, storage and use of the streams.
Boitiaux, et al in "Newest Hydrogenation Catalyst", Hydrocarbon Processing, March 1985, p. 51-59, present an overview of various uses of hydrogenation catalysts, including selective hydrogenation, utilizing a proprietary bimetallic hydrogenation catalyst. More particularly at page 56, the authors show that the only significant transformation of components is vinylacetylene to 1,3-butadiene with the improved catalysts in a stream also containing 1-butyne, 1,2-butadiene and olefins.
U.S. Pat. No. 4,067,921 discloses a process known as the Dow K Process, where acetylenes are hydrogenated in a diene stream containing principally 1,3-butadiene and trace amounts of vinylacetylene, ethylacetylene, and 1,2-butadiene, with substantial elimination of vinylacetylene with a small loss of 1,3-butadiene, but substantially no reduction in 1,2-butadiene (Table IV).
It is an advantage of the present invention that reduction of vinylacetylene, ethylacetylene and 1,2-butadiene is obtained in C.sub.4 olefin containing streams. It is a particular advantage that this may be achieved in a single reactive distillation column by using beds of function specific catalyst.